This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The main objective is to solve the structure of the EH-domain of the C-terminal Eps15 homology domain(EHD) protein, EHD1. We shall thus determine how it regulates endocytic transport and recycling of integrinand signaling receptors at the plasma membrane, and assess the impact of EHD1 on mitogenesis.A key cause of aberrant cell proliferation is the unchecked transduction of mitogenic signals by receptorslocalized to the plasma membrane. The internalization of growth factor receptors leads to attenuation ofstimulatory signals and receptors defective in endocytosis induce prolonged mitogenic effects. Subversion ofthe endocytic trafficking machinery is predicted to affect cell proliferation and lead to cancer. Recent studieshave also begun to address the endocytic itineraries of beta1 integrins, key receptors that interact with theextracellular matrix and coordinately transduce growth factor receptor signals that culminate in geneexpression, proliferation, and motility, thereby directly influencing cancer and metastatic potential.EHD1 is a central player in endocytic transport and recycling and we have recently demonstrated impairedb1 integrin recycling and localization to the plasma membrane as well as downstream events including cellspreading and migration in the absence of EHD1 (Jovic et al, manuscript submitted, Appendix I).Accordingly, the loss of EHD1 and/or its interactions with the network of proteins that regulate the endocyticmachinery disrupts normal cell function, and understanding the molecular basis by which the EH-domain ofEHD1 interacts with these regulatory proteins is a key goal of this proposal. Research in our laboratory hasidentified a novel function for EH-domains: direct binding to inositol phospholipids. However, the mode bywhich EH-domains interaction partners has yet to be determined. The proposed collaborative study will allowus to elucidate the molecular mechanisms of EHD1 function by NMR-based solution of the EHD1 EH-domainstructure, and provide novel insights into the functioning of this key protein and its regulation of integrins.